Common widely used threaded bushes are shown in FIGS. 1 and 2, having some round holes in a lower end or some vertical V-shaped grooves b spaced apart equally in an outer surface. The conventional threaded bush shown in FIG. 1 has almost the same diameter in both ends, so it does not tightly engage a hole wherein this bush is positioned after it is screwed therein. The second conventional threaded bush shown in FIG. 2, is shaped as a cone with an upper and a lower flat end, comparatively easy to move into a hole of a component, but it may loosen out because of the V-shaped grooves after a long period of use.